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One of the most powerful approaches for understanding biological invasions by non-native species is to examine ecological patterns and processes in both the native and non-native ranges of invasive species. Here’s a great article on the subject:

https://doi.org/10.1111/j.0022-0477.2004.00953.x

The number of articles published on biological invasions has increased exponentially over the last 20 years, but biogeographically explicit studies replicated in the native and non-native ranges of invasive species are still VERY rare. This hampers our mechanistic understanding of the invasion process and therefore our ability to explain, predict, and manage biological invasions.

Bromus rubens (i.e., red brome) invasion in the Mojave Desert provides a great opportunity to address this knowledge gap. We are planning to examine the individual and joint effects of shrub facilitation and post-dispersal seed predation on the abundance of B. rubens in its native (Israel) and non-native (California and Nevada) ranges. This experiment is broadly interesting because it allows us to test the relative importance of the effects of two fundamental biotic interactions on two continents. Here’s a cartoon of our experimental design:

Solid circles represent functional exclosures that effectively exclude seed predators; dashed circles represent non-functional exclosures that admit seed predators. Note the control treatment that monitors recruitment from seed banks. This is a full-factorial design that crosses shrub facilitation (open vs. shrub microsites) with seed predation (functional vs. non-functional exclosures). Pretty cool.

We will replicate this setup at 5 shrub-open pairs per site at 6 sites across the Mojave (GPS coordinates are preliminary):

Sitelatlong
Veg36.44603-114.96
Mes36.75986-114.07
Bak35.40529-115.797
HOM34.71012-115.689
Need34.49663-114.733
Palm34.16122-115.714

We will replicate the experiment at 5 sites in the Negev Desert of Israel with the help of Dr. Merav Seifan of the Ben Gurion University of the Negev. She rocks! Site locations and GPS coordinates in Israel are forthcoming.

The biogeographic contrast of the effects of seed predation can be considered a test of the enemy release hypothesis, which has only been examined once in the context of seed predation:

https://doi.org/10.1002/ece3.5314

However, the biogeographic contrast of the effects of shrub facilitation is COMPLETELY NOVEL…I think 🙂

We begin work this spring! We’ll keep you posted.